How to capture mouse wheel on panel?

To wire it up manually...

this.panel1.MouseWheel += new System.Windows.Forms.MouseEventHandler(this.panel1_MouseWheel);

private void panel1_MouseWheel(object sender, System.Windows.Forms.MouseEventArgs e)
{
    ///process mouse event
}

Easier method is in visual studio click on panel, goto properties viewpanel, select events, locate and double click the "mousewheel" event.

Windows sends the WM_MOUSEWHEEL message to the control that has the focus. That won't be Panel, it is not a control that can get the focus. As soon as you put a control on the panel, say a button, then the button gets the focus and the message.

The button however has no use for the message, it's got nothing to scroll. Windows notices this and sends the message to the parent. That's the panel, now it will scroll.

You'll find code for a custom panel that can get the focus in this answer.

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UPDATE: note that this behavior has changed in Windows 10. The new "Scroll inactive windows when I hover over them" option is turned on by default. The makes the mouse wheel behavior more consistent with the way it works in a browser or, say, an Office program. In this specific case the picturebox now will get the event. Watch out for this.

If you can't see the "MouseWheel" event on a component, then you need to create it manually. Also, we need to focus that component, otherwise the "MouseWheel" event will not work for that component. I will show you how to create a "MouseWheel" event for "pictureBox1" and how it works.

1. INSIDE THE CONSTRUCTOR, create a mousewheel event on that component.

   InitializeComponent();
   this.pictureBox1.MouseWheel += pictureBox1_MouseWheel;
   

2. CREATE THE FUNCTION manually. According to my example, call it "pictureBox1_MouseWheel"

   private void pictureBox1_MouseWheel(object sender, MouseEventArgs e)
   {
       //you can do anything here
   }
   

3. CREATE a MouseHover event on that component (Go to properties in PicureBox1, select event, locate "MouseHover" and double-click the "MouseHover" event).

4. CALL "Focus()"; method inside that MouseHover event.

   pictureBox1.Focus();
   

5. Now run the program.